This invention relates to model railroad couplers, and specifically to a centering system for such couplers.
Model railroads, as the name suggests, are scale models of prototype railroads. A complete model railroad includes a track layout, a power source, which is usually electric, non-powered rolling stock, and at least one powered engine, or powered rolling stock.
Because model railroads are scale models of prototype railroads, it is important to model railroaders that the rolling stock, whether powered or non-powered, be a precise imitation of a full scale, unit. To this end, the coupling between units of rolling stock is of critical importance.
The National Model Railway Association (NMRA) had adopted what is known as a hook-and-horn coupler as its standard. While this coupler is effective in joining units of model railroad rolling stock, it is not prototypical, in that it does not look like the coupler generally used railroads found in the western hemisphere. The NMRA hook-and-horn coupler is usually manufactured from plastic material, and includes an integrally formed centering spring mechanism. A significant problem arises when a centering spring mechanism is fabricated from any polymer material: the polymer material has a "memory". When a train has been parked on a curved section of track, with the couplers held off-center, for an extended period of time, i.e., several days, the polymer springs tend to deform, and will then be biased to that deformed condition when released. The use of metal springs virtually eliminates the problem of centering spring deformity.
A number of couplers provide prototypical appearance of couplers which are used on prototypical railroads in the western hemisphere. The most prevalent coupler is the Magna-Matic.RTM. coupler, manufactures by Kadee Quality Products, Inc., and often referred to as a Kadee.RTM. coupler. Kadee.RTM. couplers have a very realistic appearance and are also magnetically operable to provide for remote coupling and uncoupling. Kadee.RTM. couplers have been manufactured for many years and are the standard which is adopted by most model railroad clubs. One of the features of a Kadee.RTM. couplers is that it remains centered, parallel with the longitudinal axis of the rolling stock to which it is mounted, and will return to a center position even if left coupled on a curved section of track for an extended period of time. The reason that the Kadee.RTM. coupler returns to its center position is because the centering spring used in Kadee.RTM. couplers is metallic. Most Kadee.RTM. couplers use a phosphor-bronze centering spring, as depicted in FIG. 1, generally at 10. Phosphor-bronze spring 10 is formed of a single piece of metal, and includes a base portion 12, a rear portion 14, and two spring portions 16, 18, which extend from base portion 12, adjacent the forward edge 12a thereof, and which terminate even with rear portion 14. Rear portion 14 acts as a stop for spring portions 16, 18. As might be expected, phosphor-bronze spring 10 is a relatively expensive piece to manufacture, and has been known to cause a certain amount of frustration to users of the Kadee.RTM. coupler, in that it is quite small and is difficult to handle.
A number of structures have been developed in an attempt to provide a centering mechanism for a coupler which does not use a spring such as phosphor-bronze spring 10. By in large, these other devices have been formed of polymer material and have had spring components thereof extending outward from a variety of locations. The polymer springs have the problem of centering spring deformation if left on a curved track for any length of time.
Wicher, U.S. Pat. No. 2,409,920 depicts a coupler mechanism which includes a centering spring having a u-shaped contour, which is attached to the shank of a coupler by means of a clip. The clip is held in place by the same fastener which holds the coupler to the rolling stock, requiring a certain amount of manual dexterity in locating the coupler on the rolling stock.
Goode, U.S. Pat. No. 2,617,541 depicts a model railroad coupler having a variety of spring mechanisms, including leaf springs mounted on the coupler and on the draft box therefor, as well as oppositely acting coil springs, which serve to center the coupler. The coupler taught by Goode includes, in some embodiments, a multi piece shank which carry separate pieces of the coupler head thereon. Likewise, Foulkes, Australian Design Patent AU-S-121715 discloses a two piece coupler having overlaid shanks, wherein each portion of the shank carries a spring thereon, which spring coacts with the draft box.
German Patent DE4020756-C discloses a coupler having spring mechanism extending from the base of the shank thereof to provide a centering mechanism. Likewise, Staat, U.S. Pat. No. 5,509,546 and Gramera, U.S. Pat. No. D326,693 both disclose couplers which have spring mechanisms integrally formed with the shank thereof and which extend outward from the shank to provide a centering mechanism.
Many of the previous described devices are formed of plastic materials which have polymeric memory. Thus, if a train is left in a coupled conditioned and is left on a curved section of track for any length of time, the polymer material will "remember" the deformed condition of the centering springs and, when the cars are uncoupled, will continue to hold the coupler off-center. The couplers will not easily join nor easily uncouple with one-another when it s desired to form another train. This is an undesirable condition and, for this reason, such couplers are not favored by model railroaders.
It is an object of the instant invention to provide a centering mechanism which is integrally formed with the coupler.
Another object of the invention is to provide a centering mechanism which is easy to manufacture and handle.
A further object of the invention is to provide a centering mechanism which will return the coupler to a centered position, regardless of how long the coupler has been held off-center.
Yet another object of the invention is to provide a centering mechanism which maintains the coupler in a centered condition while the coupler mechanism itself is in a relaxed condition.